Two state lawmakers on Tuesday questioned the financial wisdom of merging the Demarest police force with the Bergen County Police, with one saying “The numbers simply do not add up.”

But county officials fired back, saying the deal will save a combined $4.7 million over a seven-year contract, with Demarest pocketing $2.3 million in savings.

The deal also will bolster the Bergen County Police by absorbing 13 Demarest officers, something county officials say is needed to handle an increased workload. Demarest will continue to be patrolled by two officers at a time. County officials say money will be saved on their end because those officers will be paid at their current pay scale — a lower rate than the typical county officer — for the first five years of the pact.

The to and fro among officials addressed a core question: Does the merger make financial sense for all county taxpayers, as well as those in Demarest?

In the first detailed public description of the proposal and the assumptions behind the deal, county officials estimated Demarest will save $2.3 million by contracting county police services through 2019. County officials figure to save $2.4 million during that time, mostly by filling vacancies with the current borough officers.

“It’s like any other shared service. It has to make sense for both sides,” County Administrator Ed Trawinski said.

On Monday night, the Demarest Council voted to dissolve its police force, intending to merge it with the County Police. The next step is council approval of a contract, which then would go to an ultimate vote by the county freeholders.

Freeholder Chairman John D. Mitchell said he urged the administration to make the numbers public as soon as possible. Administrators briefed the freeholders on the contract in closed session in October.

“The numbers made sense to me,” said Mitchell, who has remained noncommittal so far. “The big-picture view is that there will be significant productivity savings both for the county and for Demarest. However, until the public sees how the dollars add up, there’s going to be a lot of questions.”

The merger of a local force into the county police would be an historic first in Bergen County. But some officials question whether it means one town’s security will be subsidized by the other 69 towns in Bergen.

“I do not understand how the county can retain all of Demarest’s existing police personnel and services, currently budgeted [annually] at $3.1 million, but only charge [the borough] $2.7 million,” State Sen. Paul Sarlo, D-Wood-Ridge, wrote Tuesday to Mitchell. “The numbers simply do not add up.”

But they do, Trawinski said.

“There’s no way I, as county administrator, would recommend to the county executive that we do a shared service of this nature that benefited the people of one municipality at the expense of the other 69,” he said.

He said there are some unique reasons why the numbers work.

Pinched by state limits on tax-supported spending, more local departments have been turning to the county police for help. As a result, such calls have gone up by 58 percent in one year, Trawinski said, and the 89-member force’s overtime costs have increased. He said the county will need 10 to 15 more officers to handle that increased work. By absorbing the Demarest officers at lesser pay for the first five years and getting Demarest payments starting at $2.7 million and rising to $2.85 million in the final year, the county figures to save $2.4 million over the life of the contract.

If the contract saves Demarest $400,000 and there are no other costs, the savings are equivalent to about $227 in taxes on the average borough home, assessed at $710,000 in the first year of the contract, according to The Record’s analysis of taxable properties.

Mayor Ray Cywinski said he doesn’t know how much taxpayers will really save, “But looking at the budget, my conservative hope is that this will stabilize taxes next year. A tax decrease probably won’t happen” he added, because the community has to make up for surplus used in the budget last year.

Under the contract, the county would provide two officers on a 24/7 basis in Demarest along with the current chief, assigned to the borough as a County Police commander. The county also will provide a school resource officer and full detective and crossing guard services. The borough court would merge into the Central Municipal Court with the Demarest building serving as a satellite office.

Demarest officers will keep the current rate of pay and then begin five steps toward the new County Police compensation.

State Sen. Gerald Cardinale said he can see the benefits of the contract as a resident of Demarest, where voters approved the merger in a non-binding referendum on Nov. 6. But, he added, “As I see it, there are no economies of personnel that are available to the county. They [the freeholders] have got to check the arithmetic very carefully.”

A question Mitchell said he wants answered is how the county administration has factored in the cost of medical benefits for the Demarest officers when they retire. County officers and their families get medical benefits for life, while Demarest officers do not, Mitchell said.

Cywinski said the county has worked the deal to include such health coverage for the new officers.

Police mergers are relatively rare, but less so in recent years as municipalities have struggled to cover costs under state limits.

According to the state Department of Community Affairs, there have been at least 10 “shared” police departments formed since 2009, mostly on the local level. Department spokeswoman Tammori Petty said there are several municipalities that are currently exploring a police merger or are in the process of negotiations.

The questions raised by the lawmakers are also being posed by other municipal officials in Bergen County.

“I’d like to see if it works out and see who is paying for the merger. I don’t want to see any costs going on the backs of any of the other municipalities,” said Westwood Mayor John Birkner. “I’d like to see how it really plays out and if it’s really advantageous for the county and municipalities or is it just a special deal for Demarest.”

Norwood Mayor James Barsa, said he has mixed feelings about the proposal having been raised in Demarest.

“When the county takes over, they will lose that small-town feel, which is why people wanted to move to a town like this,” Barsa said. “I know they are doing it for financial reasons.”

He echoed concerns of other mayors that the taxpayers will have to pay for protection of Demarest. “It could be good for Demarest residents, but nobody else should be paying to protect Demarest.”